Each year, more than four million people become infected by the Human Immunodeficiency Virus (HIV), one of the many problems tackled by the 24,000 delegates at the XVI International Aids Conference held August in Toronto.
A report released by the Global HIV Prevention Working Group during the conference highlighted several approaches to HIV prevention currently being tested.
Observational reports showed that circumcised men are less likely to become infected by a female partner. A study by Dr. J.O. Lloyd-Smith from Penn State University’s Centre of Infectious Disease Dynamics used a mathematical model to predict the potential impact of male circumcision (MC) on the AIDS epidemic in Africa. They concluded that MC could avert on average two million new HIV infections, particularly in southern Africa where MC is uncommon and HIV is prevalent.
Another prevention strategy, pre-exposure prophylaxis or PREP, involves giving HIV-negative people (those not infected) antiretroviral drugs. Traditionally, antiretroviral drugs are used to treat HIV infections. Though activists protested the use of the PREP at the XV International AIDS Conference, sites in Thailand, Botswana, and Peru are testing the drug tenofovir for its efficacy.
Presented as a promising approach, microbicides are geared for topical usage, in gels or creams, which are applied to the vagina or rectum. They may reduce transmission of HIV by up to 60 per cent. Some microbicides work to enhance the vagina’s natural acidity and prevent transmission. Others include surfactants that break up membranes, like the viral envelope, to disable the virus and prevent infection. Five microbicides are currently being tested with several more in earlier phases of clinical trials.
While five years is the soonest prediction for approved microbicide use, most experts predict that it will be more than ten years before a fully effective HIV vaccine will exist. Currently, 30 HIV vaccine candidates are in the product pipeline. The ‘subunit’ approach to vaccines, favoured in HIV research, introduces a fragment of an inactivated or weakened virus to elicit an immune response.
Other prevention strategies include use of cervical barriers, such as the diaphragm, and suppression of herpes infection, which triples risk of HIV infection.
A multi-institutional research consortium, the Elite Controller Collaborative Study, will study natural HIV suppression by the human immune system. Dr. Bruce Walker, director of Partner AIDS Research Centre at Massachusetts General Hospital described “elite controllers” as people infected with HIV who are able to suppress the virus without any medication, remaining healthy and symptom-free.
Researchers estimate that one in 300 people infected with HIV are able to suppress the virus naturally, keeping the number of virus copies in the body low enough to be without symptoms. The goal of the consortium is to identify and explain the mechanism that controls viral replication. A vaccine built on this premise may not prevent infection, but may suppress viral replication and be useful in AIDS treatment.
Since the pandemic began 25 years ago, advances in treatment have improved patient life quality. Pill dosage has been reduced from ten pills a day ten years ago to just one today. Until a truly effective HIV vaccine exists, the best treatment lies in the prevention of infection.
